Left: same as Fig. 4 in the case of CMB. POKER’s estimation is unbiased but mask aliasing induces strong correlations between bins at high k where the power spectrum is very steep. Right: this time, the mask with apodized boundaries (bottom of Fig. 2) is used. High k bin-to-bin correlations are significantly reduced. Apodization however reduces the effective observed fraction of the sky and therefore slightly increases error bars at low k compared to the plots on the left. Note that although apodization also improves the “naive” estimate, it remains not compatible with the input spectrum for almost every bin and to more than the 1σ error of a single realization.